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21.
Rodnina M. V. Semenkov Yu. P. Savelsbergh A. Katunin V. I. Peske F. Wilden B. Wintermeyer W. 《Molecular Biology》2001,35(4):559-568
During the translocation step of the elongation cycle of peptide synthesis two tRNAs together with the mRNA move synchronously and rapidly on the ribosome. Translocation is catalyzed by the elongation factor G (EF-G) and requires GTP hydrolysis. The fundamental biochemical features of the process were worked out in the 1970–80s, to a large part by A.S. Spirin and his colleagues. Recent results from pre-steady-state kinetic analysis and cryoelectron microscopy suggest that translocation is a multistep dynamic process that entails large-scale structural rearrangements of both ribosome and EF-G. Kinetic and thermodynamic data, together with the structural information on the conformational changes in the ribosome and EF-G, provide a detailed mechanistic model of translocation and suggest a mechanism of translocation catalysis by EF-G. 相似文献
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Sivakoti Ramana Ashis Kumar Biswas Amar Bahadur Singh Ajay Narendar Kumar Ahirwar Annangi Subba Rao 《International journal of phytoremediation》2015,17(4):363-368
The potential of an ornamental shrub Crown of thorns (Euphorbia milli) was evaluated for remediation of soil contaminated with Cr. The plant is one of the rare succulent ornamental shrubs with a slow to moderate growth rate and is capable of blooming almost year-round. The plant could tolerate well up to 75 mg of applied Cr and beyond that there was mortality of plants. Though the plant could not be classified as a hyperaccumulator, the plant was still very efficient in translocating Cr from roots to shoots as evident from the data on uptake and translocation efficiency values. The translocation efficiency of over 80% in our study demonstrates that a large proportion of Cr has been translocated to the harvestable biomass of the plant and therefore, this plant could be effectively recommended for the remediation of soils contaminated with low to medium level of contamination i.e., up to 50 mg/kg soil. 相似文献
25.
Ignatova Z Hörnle C Nurk A Kasche V 《Biochemical and biophysical research communications》2002,291(1):146-149
The recently described Tat protein translocation system in Escherichia coli recognizes its protein substrates by the consensus twin arginine (SRRXFLK) motif in the signal peptide. The signal sequence of E. coli pre-pro-penicillin amidase bears two arginine residues separated by one aspargine and does not resemble the Tat-targeting motif but can nevertheless target the precursor to the Tat pathway. Mutational studies have shown that the hydrophobic core region acts in synergism with the positive charged N-terminal part of the signal peptide as a Tat recognition signal and contributes to the efficient Tat targeting of the pre-pro-penicillin amidase. 相似文献
26.
Vacuoles isolated from the storage roots of red beet (Beta vulgaris L.) accumulate sucrose via two different mechanisms. One mechanism transports sucrose directly, and its rate is increased by the addition of MgATP. The other mechanism utilizes uridine diphosphate glucose (UDP-glucose) to synthesize and simultaneously transport sucrose phosphate and sucrose into the vacuole. This group translocation mechanism has also been found in sugarcane vacuoles. As in sugarcane, the beet group translocator does not require fructose 6-phosphate, nor is the latter substance transported into the vacuole. The uptake of UDP[14C]glucose in inhibited by high concentrations of osmoticum.Abbreviations EDTA
ethylenediaminetetraacetic acid
- Hepes
4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid
- UDP
uridine 5-diphosphate 相似文献
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28.
F. R. Murray J. H. Skerritt R. Appels 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2001,102(2-3):431-439
A genomic DNA clone coding for a rye secalin gene (gSec2A) was isolated from a wheat translocation line carrying the 2RS.2BL
chromosome, using a previously identified partial secalin (Sec2) cDNA clone as a probe. The predicted N-terminal amino-acid
sequence of the gSec2A gene was identical to the N-terminal sequence obtained for Sec2 polypeptide bands isolated from SDS-PAGE
gels. Bacterially expressed gSec2A protein was identical in size to that of the smallest Sec2 polypeptide band observed on
SDS PAGE gels and is recognized by a monoclonal antibody specific for Mr 75000 2RS γ-secalins. Overall, the predicted protein
sequence of gSec2A was most similar (50%) to the family of γ-gliadins and consists of a short N-terminal region containing
one cysteine residue followed by a glutamine/proline-rich repetitive domain and a long C-terminal domain containing eight
cysteine residues. The repetitive domain can be divided into two regions. One region coded for 15 units, each consisting of
eight amino acids similar in sequence to that found in the ω-secalins and C-hordeins. The second region coded for 17 units
each consisting of a sequence of 7–10 amino acids similar to that observed in γ-gliadins.
Received: 31 February 2000 / Accepted: 21 May 2000 相似文献
29.
Background and Aims
Anoxic conditions are seldom considered in root iron plaque induction of wetland plants in hydroponic experiments, but such conditions are essential for root iron plaque formation in the field. Although ferrous ion availability and root radial oxygen loss capacity are generally taken into account, neglect of anoxic conditions in root iron plaque formation might lead to an under- or over-estimate of their functional effects, such as blocking toxic metal uptake. This study hypothesized that anoxic conditions would influence root iron plaque formation characteristics and translocation of Zn and Cd by rice seedlings.Methods
A hydroponic culture was used to grow rice seedlings and a non-disruptive approach for blocking air exchange between the atmosphere and the induction solution matrix was applied for root iron plaque formation, namely flushing the headspace of the induction solution with N2 during root iron plaque induction. Zn and Cd were spiked into the solution after root iron plaque formation, and translocation of both metals was determined.Key Results
Blocking air exchange between the atmosphere and the nutrient solution by N2 flushing increased root plaque Fe content by between 11 and 77 % (average 31 %). The N2 flushing treatment generated root iron plaques with a smoother surface than the non-N2 flushing treatment, as observed by scanning electron microscopy, but Fe oxyhydroxides coating the rice seedling roots were amorphous. The root iron plaques sequestrated Zn and Cd and the N2 flushing enhanced this effect by approx. 17 % for Zn and 71 % for Cd, calculated by both single and combined additions of Zn and Cd.Conclusions
Blocking of oxygen intrusion into the nutrient solution via N2 flushing enhanced root iron plaque formation and increased Cd and Zn sequestration in the iron plaques of rice seedlings. This study suggests that hydroponic studies that do not consider redox potential in the induction matrices might lead to an under-estimate of metal sequestration by root iron plaques of wetland plants. 相似文献30.
F Mercier H Reggio G Devilliers D Bataille P Mangeat 《Biology of the cell / under the auspices of the European Cell Biology Organization》1989,65(1):7-20
A monoclonal antibody (mab 146.14) marker of the movement of acid-secreting membranes in rat gastric parital cells has been produced and characterized. Mab 146.14 recognized a 95-kD major component of a purified membrane fraction of rat gastric mucosa, the protein composition of which was similar to that of well characterized porcine H+ -K+ ATPase-enriched membranes, and that presented the characteristic shift of density depending on whether it was purified from resting or stimulated tissues. Further biochemical analysis characterized the antigen as a membranous protein that might be in its native form, part of a higher multimolecular complex. Immunocytochemical localization of the antigen demonstrated that only membranes related to acid secretion in parietal cells expressed the 95-kD antigen. In resting conditions, the 95-kD antigen was diffusely distributed in the cell cytoplasm associated with inactive tubulovesicles. In stimulated cells, by contrast, all the antigen was recovered associated with secretory active microvilli formed by the apical insertion of the previously resting internal tubulovesicles. In conclusion, the 95-kD antigen, presumably a part of the rat gastric proton pump, is a marker of acid-secreting membranes in rat parietal cells. The translocation of antigen and membranes, observed by both light and electron microscopy supports the fusion model of membrane insertion from a cytoplasmic storage pool to the apical surface upon stimulation of acid secretion. 相似文献